Source routing is a mechanism to forward a packet through a network or network segment with no per path state provided at tandem devices (i.e., the devices or nodes within the network that are neither the ingress node nor the egress node of the source routed segment). In many systems, source routing is enabled by information contained in a source route header. A source route header typically contains an explicit list of links to follow, or a strict or loose list of nodes to follow in various encoding formats. Often the path that a packet should follow must be changed for administrative or operational reasons.